The preparation of textured α-Al2O3 layers, produced with chemical vapour deposition (CVD), is disclosed in e.g., EP 603144, EP 1528125, EP 1477581, EP 659153, EP 1655387, EP 659903, EP 738336, EP 1655388, EP 1655392, US 2007/104945, and US 2004/202877.
EP 1479791 discloses a cutting tool containing cemented carbide or cermet, and a hard coating; wherein the hard coating includes an α-Al2O3 layer formed by CVD, with the highest peak, measuring the inclination of the α-Al2O3 basal planes relative to the normal of the surface within a range of 0-10 degrees as determined by electron back scattering diffraction (EBSD).
EP 744473 discloses textured γ-Al2O3 layers produced by PVD.
U.S. Pat. No. 5,310,607 discloses a hard coating including (Al,Cr)2O3 crystals and a chromium content higher than 5 at % wherein the (Al,Cr)2O3 is a single crystal. The coating is deposited at a temperature lower than 900° C. The hard coating is deposited by a CVD or PVD process.
When machining with an alumina coated cemented carbide tool, the cutting edge is worn according to different wear mechanisms, such as chemical wear, abrasive wear, adhesive wear and by edge chipping caused by cracks formed along the cutting edge. The domination of any of the wear mechanisms is determined by the application, and is dependent on properties of the machined material, applied cutting parameters and the properties of the tool material. In general, it is very difficult to improve all tool properties simultaneously, and commercial cemented carbide grades have usually been optimised with respect to one or few of the above mentioned wear types, and have consequently been optimised for specific application areas. This can, for instance, be achieved by controlling the texture of the alumina layer.
What is needed is a wear resistant and hard oxide coated cutting tool with enhanced performance for machining of cast iron. The invention is directed to these, as well as other, important needs.